Cargo trailers are vehicles that typically are towed behind pick-up trucks and large automobiles, for the most part. Cargo trailers can also be towed behind larger vehicles, including large recreational vehicles, and the like. A cargo trailer itself could be considered a recreational vehicle in many cases, although by definition a cargo “trailer” would not be self-propelled, but would be towed.
Vehicles such as cargo trailers, and perhaps other types of recreational vehicles such as campers, are typically constructed using a set of bottom frame rails, and four corner vertical supports or “posts.” The vertical supports can then hold a top horizontal edge or corner rail along each side of the cargo trailer and, if desired, also horizontal rails along the rear-top corner and the front-top corner of the trailer. The elongated longitudinal sides are typically made of aluminum sheet material, although other types of materials could be used if desired. Such sheets of material are typically screwed into position by being mounted on multiple, parallel vertical supports that run between the top elongated edge rail and the bottom elongated edge rail of one side of the trailer. These parallel vertical supports are often referred to as “rails” or “ribs.” In the case of many cargo trailers built in the United States, these vertical ribs are spaced-apart by a constant distance, such as sixteen inches or twenty-four inches, between centerlines of the vertical ribs. In many cases, the ribs are in the form of a type of U-channel, which also is referred to as a “hat” channel by many manufacturers of cargo trailers. When viewed in cross-section, such hat channels have the appearance of a top hat with a rim on both sides. (See FIGS. 3 and 4 for an example of such a cross-section of a hat channel.)
Many manufacturers of cargo trailers use aluminum sheets that are approximately 4-8 feet wide, and 6-10 feet tall, depending on the height of the trailer. The sheets are typically screwed into the hat channels at a constant spacing in the vertical direction, and the spacing between the screws is typically five inches between the centerlines of the screws. This of course can be adjusted to a different distance, if desired. The conventional method for determining the positions of the screws is for the trailer manufacturer to mark a grid across the exterior surface of the aluminum sheet material using blue lines or some type of chalk lines to mark vertical positions and horizontal positions, thereby creating an X-Y grid of the screw locations. The vertical lines indicate the position of one of the hat channels that will be behind the aluminum sheet as the aluminum sheet is screwed to the hat channel. The horizontal lines indicate the (vertical) spacing between the screws going down the hat channel location. Some cargo trailers use ribs that go around both walls and also across the top of the body of the trailer, and in that situation the top of the trailer will also have aluminum sheet material screwed into similar hat channels that are run horizontally across the roof of the trailer, between the two elongated top horizontal rails that form the left and right longitudinal edges of the trailer framework. The ribs themselves could even be bent into a U-shape to form the walls and top of a body, or they can be made of separate linear pieces of hat channel material, if desired.
Referring now to FIG. 1, a side view of a conventional cargo trailer is depicted, showing its right side before an outer skin made of aluminum body panels is applied to the framework. The overall structure is generally referred to by the reference numeral 10, while a rear vertical corner post is at 20, and a front corner post is at 22. These posts essentially are vertical members, although trailers can be constructed with non-vertical front and rear surfaces, if desired. In FIG. 1, there are multiple parallel hat channel ribs generally designated by the reference numerals 30, and these are typically spaced-apart from one another by a predetermined distance “S1”. While it is not always necessary to use the same spacing between each of these vertical ribs, it is typically done for ease of construction. In FIG. 1, the trailer 10 also has other vertical support members designated at the reference numerals 32, which may or may not be constructed of the same type of hat channel material. These other vertical supports could be any appropriate type of material desired by the manufacturer, such as angle or Z-ribs, if desired. In fact, all of the side supports throughout the trailer (vertical supports, or otherwise) can be Z-ribs, if desired.
In the trailer 10, there is an elongated top frame member 24 that is visible extending between the rear corner post 20 and the front corner post 22. This top frame member 24 is generally horizontal, until nearing the front corner post 22, at which time the top frame member angles down, as can be seen in FIG. 1. It should be noted that the top frame members along the top left and right corner edges of the trailer can be entirely horizontal, if desired by the designer, or can be segmented at various angles, if desired. For example, the slope in the front-most frame member portion near the front corner post 22 only runs a small distance in FIG. 1, however, on some cargo trailers the roof portion of the cargo trailer begins to slope downward at a position much closer to the mid-point between the front- and rear-most portions of the trailer. Again, this is a matter of design choice.
In FIG. 1, there are also bottom frame members generally designated by the reference numeral 26, which extend along the bottom right edge of the framework. These frame members 26 are generally horizontal in FIG. 1, although it can be seen that the rear-most bottom frame member 26 extends downward toward the rear corner post 20. Again, the exact angles are a matter of design choice.
In the trailer 10, there are a few openings 40 for windows, as well as a cargo opening 42, a furnace opening 54, and also openings for vents at 50 and for a vent door at 52. The “straight” longitudinal run of the bottom frame members 26 is interrupted at a wheel well 44. Again, this is a matter of design choice, although wheel wells are fairly standard in conventional cargo trailers. It should be noted that the windows and cargo openings are optional in the side walls of a cargo trailer; this is a matter of design choice.
Referring now to FIG. 2, a hat channel rib 30 is depicted in a side view, and also shows the conventional construction of the outer skin which is typically made of aluminum sheet at 60, and the inner lining at 64 is typically made of a relatively thin laminate material, such as plywood (also known as “luan”). A pair of screws 62 are depicted in FIG. 2, and are shown in their inserted position through the aluminum sheet material 60 and through one of the members 34 of the hat channel 30. This portion 34 of the hat channel can be referred to as a “base leg portion,” which is better viewed in FIG. 3, which illustrates the hat channel 30 in cross-section. In FIG. 3, it can be seen that the hat channel 30 has a U-portion 36, and two base leg portions 34. Referring back to FIG. 2, the spacing between the centerlines of the screw 62 is referred to as a distance “S2”. This distance S2 typically would be a vertical distance along one of the ribs 30, when viewed from the perspective of FIG. 1.
In FIG. 3, the aluminum sheet material is at the top-most portion of the view, and the thin plywood 64 is at the bottom-most portion of the view. Numeral 66 on FIG. 3 designates a location where a screw could be placed to hold the thin plywood 64 to the hat channel rib 30.
Referring now to FIG. 4, the rib 30 could still be made of the same hat channel material, but used in its opposite direction. In FIG. 4, the U-portion 36 is directed toward the aluminum sheet material 60, while the two base leg portions 34 are directed toward the thin plywood material 64. In this construction of FIG. 4, there are two locations 66 where a screw could be placed through the thin plywood 64 and into the hat channel rib 30, if desired.
Referring now to FIG. 5, a different form of rib material is illustrated by the reference numeral 70. In this view, a Z-angle material is used, and the screw 62 is placed in one of the two horizontal (in this view) portions of the Z-angle rib. The opposite horizontal portion (in this view) will give rise to having a screw placed at the location 66, to hold the thin plywood 64 in place against the Z-angle 70. Naturally, other shapes of ribs could be used than the hat channels 30 and Z-angles 70 depicted so far in the drawings.
When using conventional construction techniques, the trailer fabricator must place the aluminum sheet in a position between the top and bottom side (edge) frame rails (or supports), and then screw the individual screws into the aluminum sheet and into the hat channel, at the appropriate locations. Since the locations are marked on a grid, the worker knows exactly where he or she is supposed to place the screws that are to penetrate the aluminum sheet and the hat channel. However, most conventional trailer manufacturers use hand-held screws along with automatic screwdriver tools, and there is no “good” way to ensure that the screw will actually penetrate the aluminum sheet accurately at the appropriate location, and worse, there is no assurance that the screw will not slip as it attempts to enter the aluminum sheet, and then possibly scratch the surface of the aluminum sheet. Since many of the cargo trailers are painted various colors (such as a dark red color) on the outer surface of the aluminum sheet, a slipped screw will likely scratch the sheet and essentially ruin its appearance. When that occurs, the worker will typically be required to unscrew all of the previously placed screws for that particular aluminum sheet material, and remove that particular body panel (aluminum sheet) from the side of the trailer, and start over with a new aluminum sheet. This can greatly increase the manufacturing time, particularly if the worker had already installed most of the screws required for that particular sheet of aluminum material. It would be an improvement to use an automatic screwdriver tool that can accurately place the screws at the appropriate locations in the aluminum sheet, and which will ensure that the screw will be properly driven through the aluminum sheet and into the hat channel, without a significant chance of slipping and scratching the outer surface of the aluminum sheet.